וְאֶת־אַהֲרֹ֥ן וְאֶת־בָּנָ֖יו תִּמְשָׁ֑ח וְקִדַּשְׁתָּ֥ אֹתָ֖ם לְכַהֵ֥ן לִֽי׃
And thou shalt anoint Aaron and his sons, and sanctify them, that they may minister unto Me in the priest’s office.
Read kabbalistic (mystical) interpretation of Exodus 30:30: and classical mystical sources.